GB645526A - Improvements relating to the detection of leakage into vacuum systems - Google Patents

Abstract

645,526. Electric indicating systems. BLEARS, J., LECK, J. H., and METROPOLITAN-VICKERS ELECTRICAL CO., Ltd. Nov. 29, 1948, No. 30932. [Class 40 (i)] In apparatus for detecting leaks in a vacuum system by the external application of a preselected gaseous probe medium, a copper block 1 (Fig. 1) has a central chamber 2 which is sealed at 7 and connected to the vacuum system through a constriction 9. Side chambers 3, 4 contain Pirani resistance gauges 5, 6, and are connected through constrictions 13, 14 to opposite ends of the central chamber which is packed with hydroxide of calcium or other alkaline earth metal to absorb the carbon dioxide probe medium. The constrictions are such that the chambers have equal gas flow time constants, and the Pirani gauges are connected in a normally balanced. bridge network (not shown). Air leakage into the system affects both gauges equally so that bridge balance is preserved, but on external application of the probe medium the latter diffuses into the chamber 4 but is retained by the absorbent barrier, thus reducing the pressure in chamber 3 to produce a bridge unbalance which is a measure of the leakage. Other gases may be used as probe media, with appropriate absorbents, and the electroresponsive gauges may be of alternative types, e.g. ionization gauges. In a modification (Fig. 2, not shown), the gauge chambers may be separately connected to a common conduit, and the absorbent interposed in the appropriate connection..